Signaling system



Oct. 27, 1942. w. H. T. HOLDEN SIGNALING `SYSTEM Filed April 26, 1941 6 sheps-sneet 1 WWW@ A TTONE V Oct. 27,1942. w. H. T. HoLDl-:N 21,299,897 l l SIGNALING SYSTEM l Filed April 2e, 1941 e sheets-sheep 2 /NVE/vro@ WH. 7. HOLDEN .8 www@ ATTORNEY Oct. 27, 1942. w. H. T. HOLDEN 2,299,897

SIGNALING SYSTEM Filed .April 26, 1941 6 Sheets-Sheet 5 SEA/DER SEA/DER W H HOLDEN wrm? Oct. 27, 1942. w. H. T. HOLDEN 2,299,897

l SIGNALING SYSTEM l Filed April 26, 1941 6 Sheets-Sheet 4 REG/srE/Qs SENDER BV WH/N1' HOLDEN Arron/viv 6 Sheets-Sheet 5 ovwLl glw,

W. H. T. HOLDEN SIGNALING SYSTEM Filed April 26, 1941 oct. 27, 1942.

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-lww IPIIIII-II Patente'd Oct. 27, 1942 y 2,299,897 STGNALIING SYSTEM William H. T. Holden,

Woodside, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New

York, N. Y., a corporation of New York Application April 26, 1941, Serial No. 390,456

. 9v Claims.4 (Cl. 179-18) This invention relates to electric signaling and particularly when used in automatic telephone or other communication systems.

The objects of the invention are to simplify the transfer of signal information from one part of a signal system to another; toA eliminate much `of the connecting equipment heretofore used for establishing the signaling circuits; `to utilize the same transmitting paths for sending a plurality of sets of signals simultaneously; to increase the speed of transmitting signal information; and in other respects to improve signaling systems.

It has been the practice heretofore in automatic telephone systems to provide connectors for establishing individual connections between the mechanisms of one group, such as senders, and the mechanisms of a second group, such as switch controlling markers. Byvproviding these connecting devices it is possible to establish a plurality of electrically separate simultaneous connections between a number of senders and a corresponding number of markers. These connectors, however, are expensive since they involve a large amount of equipment, particularly if the sender and marker groups are large. If multiu contact relays are employed for establishing the connections, it is usually necessary to provide a relay for each sender in the sender group and one for each marker in the marker group. Similar connecting devices are also required in other `parts of `an automatic telephone system. For

example, in a system of the crossbar type these connectors are used to establish controlling circuit connections between the switch frames and the common controlling mechanisms or markers.

In accordance with the present invention substantial savings and other advantages may be realized over these prior systems by eliminating to a large extent the connectingequipment bei tween the different controlling mechanisms and by establishing these connections on a permanent basis. `More specifically the foregoing objects of the invention are realized by means of a signaling system in which the individual mechanisms of a group, such as a sender group in an automatic telephone exchange, are connected permanently to all of the individual controlling mechanisms of a second group, such as the group of switch controlling markers, and in which a system of multipleX signaling is employed for transmitting information concurrently from any number of senders in said group to the corresponding markers which have been selected to serve the respective senders. By means of a relatively simple selecting circuit arrangement each calling sender seizes for its use an idle one of said markers. The signal information is transferred from the sender to the marker by means of impulses, each of the markers being served by the impulses of a particular phase. When, therefore, a marker is seized by a calling sender, impulses of the corresponding phase are transmitted from the sender over the common connecting medium between all senders and markers and are received and recognized only by the associated markers. Therefore, several signaling channels may exist concurrently between senders and markers, and the mon switch controlling markers.

information pertaining to each sender and its associated marker is transmitted over the common connecting medium without interference with other channels. l l

Another featurek ofthe invention is a system in which the common signaling medium between the group of senders and the group of markers is constantly undergoing a test to determine whether it is in proper condition for the transmission of signals between the senders andthe markers.

The foregoing and other features of the invention will be discussed lmore fully in detail in the following specification.

In the drawings accompanying the specification:

Figs. 1 to 6, when arranged as illustrated in Fig. 7, disclose an automatic telephone system incorporating the features of the invention;

Fig. 1 illustrates in diagrammatic manner the line switch and certain of vthe selector switches of an automatic telephone exchange and also a sender link switch for associating the calling lines with idle common register senders;

Fig. 2 shows a portion of one of the common register senders;

Figs. 3 and 4 illustrate mon register senders; 1

Fig. 5 illustrates a portion of one of the com- 'Ihis figure also shows a common impulse generator for supplying impulses to` transfer the designations from the senders to the markers; and

Fig. 6 illustrates a second one of the common markers and also discloses alarm equipment common to all of the senders and markers.

The present invention in its broader aspects relates to the transfer of signal information over a common medium between the senders'or other devices of one group and receivers or other devices of a second group, and it should be understood that sai-d invention is not limited in its application to telephone systems or to systems of two more of the comany other particular type. It is, however, especially useful in automatic telephone systems where registered designations and other kinds of information must be transferred from one part of the system to another during the controlling operations incident to the establishment of the desired connections. Therefore, the invention has been illustrated herein when applied to the common register senders and the common switch controlling markers of an automatic telephone eX- change system of the well-known crossbar type.

For a better understanding of the various operations involved in these systems and of the details of the equipment used, reference maybe had to numerous patents, including the patents to W. W. Carpenter No. 2,093,117, September 14, 1937, and No. 2,235,803, March 18, 1941. Y

Referring to the drawings, the subscribers lines appear in the crossbar line switches |00 and through these switches have access over trunks |0| to the district selector switches |02. The district selectors have access over trunks |03 to oiice selector switches |04, and these in turn have access to the groups of outgoing trunks |05. The calling lines also have access through sender link or selector switches |06 to the common register senders which receive and store the telephone designations.

Three of these senders 200, 300 and 400 are illustrated in the drawing, and as many more l would be provided as are needed to handle the trac through the ofiice. The senders are seized at random in response to calling lines, and receive and register the designations transmitted from the calling substations. senders transfer these registered designations to the common switch controlling markers, which in turn make use of the designations received from the senders to determine and control the selective operation of the automatic switches;

' Two of the common switch controlling markers 500 and 600 are shown in the drawings, and as many more may be provided as are needed.

In the systems of the prior art, as hereinbefore mentioned, connecting devices are required for selectively connecting a calling sender with an idle one of the common markers. If, for example, four or ve senders are in use concurrently, each serving a calling line, these connecting devices serve to establish individual and separate connections between each of the calling senders and each of the associated markers. In this wa-y the designation information may be transmitted at the same time from as many of the senders as there are markers to the corresponding markers, and no interference results because the connections are separate from each other. In the present system, however, these intermediate connecting devices between senders and markers have been eliminated, and a common transmitting medium comprising the conductors 2| 0 is connected permanently and in multiple between all of the senders 200, 300, 400, etc., and all of the common markers 500, 000 etc. As above mentioned, and as will be explained more fully hereinafter, the signal information for a plurality of senders, which may be taken for concurrent use, is transmitted over` the common medium 2|0 to the respective markers without mutual interference by the use of impulse signals having different phases or time periods.

Each of the register senders includes registers for the cnice and numerical portions of the telephone designations, means Thereafter the for transmitting the* oiice registration over the common medium to the associated marker, the usual means for transmitting the numerical designations to distant senders, together with controlling relays and circuits. Two oiice code registers 20| and 202 have been shown in full in the sender 200, the assumption being that the office part of the designation consists of two letters or other characters. Two groups of transmitting tubes 203 and 204, associated with the registers 20| and 202, respectively, serve to transmit the office registration over the conductors of the common medium 2|0 to the associated marker. These tubes are of any suitable type, such as those having two electrodes and envelopes filled with some inert gas. The purpose of these tubes is to prevent the formation of sneak circuits resulting in interference between the senders and markers. Since the senders and markers are all multipled to the common set of conductors 2|0 it would be possible, with two senders having the same registration and concurrently associated with the respective markers, to trace a circuit through the contacts of the operated register relays in both senders through the corresponding register tubes of both markers in series with the impulse circuits of the two phases representing said markers. In this case both phases would be effective in operating the register tubes in both markers. To prevent this interference the transmitting tubes 203 and 204 are inserted in the transmission leads `associated with the register relays of each sender. Although the circuit above mentioned still exists it includes two of these transmitting tubes in series, whereas the voltage applied is suflicient to operate only one tube. Therefore, in any phase position the transmitting tube of the corresponding sender` and marker is operated to effect the transmission of the registration between that sender and marker without interference with other senders and markers that may be in use concurrently.

In a similar manner the remaining senders 300, 400, etc., are equipped with cnice code registers and transmitting tubes. These registers and tubes 30|, 302 in sender 300 and 40|, 402 in sender 400 are illustrated diagrammatically.

Although the information passes from senders to markers over a permanently established common medium, it is necessary to associate each sender that is taken in use with only one of the markers. Any marker may be taken by a calling sender, provided the marker is idle; and, once it has been taken by a particular sender, it cannot be seized'or appropriated by any other sender until it has performed its function. Accordingly, each of the senders is equipped with a marker alotting mechanism comprising a plurality of pairs of relays, one for each of the markers to which the sender has access. Four of these relay pairs are illustrated in the allctter mechanism 205 of the sender 200. The first pair of relays, relays 206 and 207, are individual to the No. 0 marker 500; the second pair of relays, 208 and 209, are individual to the No. 1 marker not shown; relays 2|3 and 22| are individual to the No. 2 marker 600; and the remaining pairs of relays are individual to the remaining markers, respectively. In like manner, the senders 300 and 400 are provided with marker allotting relays 305 and 405. The senders are also provided with start wires 2||, 3H and 4H which enter the allotter relay chains at diierent points so that the senders have different preferences for the markers.

" senders.

lay `registers 50`I and .502 for registering the otlice code digits and Withccrresponding sets of tubes 503 and 504 for receiving from the sender the designation signalswhich loperate these reg-- isters. These tubesmay also be of the gas-filled type or of any desired type.y It will `be noted `that each tube has a separate starting gap, comprising starting anode and cathode, as well as a main anode and cathode. `The marker 500 is also provided with a routing and controlling I mechanism 505, which is operated in accordance with the digits received by the registers 50|and 502, and which then serves in the well-known vmanner to determine the selective operation of the district and Oiiice'switches |02 and |04'.

The phase impulses by which the signal information is transferred from the senders to the markers are produced by a common impulse gen' lerator 540. plied from an alternating current source 54 I, and

The energ-y for this generator is supthe generatorin response to each cycle of the 4,source 54| produces impulsesof a given phasein `each one of the output circuits 5,42, 543, 544, 545, 546 etc., the impulses in each circuit being `of a phase differing from that in each of the other circuits. Each *one of the output circuitsfrom the generator `540 correspondsto and identifies a particular one ofthemarkers; there is, there-` fore, an output circuit foreach marker to be served by the generator.` For example, the im-` pulse circuit 542 pertains tothe marker 500; and,

`when some one of-the-` senders has vseized the r marker 500, thephase impulses produced in the conductor 541 of circuit 542; are transmitted from the sender, in accordance withvthe settings of the impulse registers, over the common medium 2I0 ,to the receiving tubes 503 and 504 of the marker. y These impulses are effective to operatey these tubes, since impulses `of the same phase are also being applied to said tubes over rthe other conductor 548 of theimpulse` circuit542. Although the impulses transmitted from the impulse conductor 541 through the calling sender andover the common mediumare alsoapplied to the rel,ceiving `tubes of all other markers at the same time, the tubes in the other markers are unresponsve because theyae not receiving impulses i of the same phase from conductor 548.

In like manner the impulses produced in the conductors of circuit 544 are transmitted over,` the common `medium from a sender tothe marker 600, provided this marker `is engaged by some one vof the The impulses onthecircuit 544, however, are in a phase differing from those'of the other impulse circuits; therefore, the information transferred to the marker 600 does not interfere with or cause the false setting of any of the Similarly, the impulse circuits 543, 545, 546, etc., serve the corresponding markers.

The impulse generator ,540 may be of anysuit# able type whereby brief impulses of positive and other markers.

negative polarity in each of a plurality of phases are generated during each cycle of the exciting source 54|. Generators ofthis type are illustrated in the application ofV W, H. T. Holden, Se-

rial No. 361536, led October 17, 1940; and the patents to W. H. T. Holden, No. 2,285,815 oi June 9, 1942, and No. 2,252,766 f Aug. 19, 1941.

. verify that they are intact and in proper condi-- tion for transmitting the designation signals. To

'10 mon to the Velectrodes of a group of ten dis--v i charge tubes` 6I5; andv the other electrodes of these tubes are connected at a point ynear the senders to the ten' conductors respectively of the i transmitting medium 2 I 0. By selecting the phase circuit 549 of the generator 540,` Whichis not used for transmitting signals to the markers, an impulse is transmitted once per cycle of the source 54|.` through the tubes 6I 5`and over the respective conductors 2 I 0 to the control gap electrodes of all goten of the tubes 6I0. The control or startgaps of `these tubes are ionized in response to each impulse received, and current flows in the main discharge vgaps of the tubes at each ionization there-v of. The main discharge circuits of the tubes 6I0 are provided With individualslow release relays 603, 604, etc., and `these relays remain operated as long as the ionizing impulses continue to appear on the respective conductors 2I0. If, however, any one of these condensers is broken or becomes `defective in other respects and the img pulses ceaseto appear thereon, the corresponding tube 6 I 0 remains deionized, and the associated ref slay releases and closes an alarm circuit.`

j I. The tubes of the groups 6I0 and SI5 may be of th `same types as ,the tubes disclosed in Figs. 2

` terminating `resistors is to stabilize the voltagesv onlthe transmitting conductors 2 I 0 and to prevent i false'sig-naling due to the accumulation of poten- Ltials` `that `might otherwise appear thereon.

The. .opera-tion of the transmitting system will 4.5 now'be explained in detail. For this purpose it i may be assumed that a callis made by the subscriber of. line` |08.` The call by this subscriber causes the; operation ofthe line switch |00 to eX- tend the line lover anidl'ejunctor I0| tothe district selector |02 andalso through the sender l selector 4svvit'ch |06 to an idle one of the register senders, such as the sender 200. Upon the seizure ofthefsender the start relay 2 I 2 operates and applies ground to the.v start `conductor ZII.` If at thistime allor' the markers are idle, the allotterv relays 206, 200,-2I3` and'2I4 are in their normal A,deenergized condition.` The grounded start conductor 2| therefore is extended through the contacts .of relay 206` andthe Winding of relay 201 to battery. Relay20'I operates and closes a circuit from ground through Aits inner upper frontwconl tact, resistor 2 I5, conductor 2 I6,` thence in parallel n throughresistor 306, normal contacts of relay v301, lower Winding of relay308 to battery and through resistor 406, normal contacts of relay 401, lower` winding of relay 408 to battery and over corresponding parallel circuits through the make-busy relays of the allotters in all other senders. The

` relays 308 and 408 in senders 300 and 400 operate and` extend their start Wires to the relay individual to the next marker. Relay 201 at its uppermost back contact'removesbattery potential from conductor 2|'I to prevent operation of the i corresponding relay injanyof the other senders. f 75Re1ay 20'I also extends the phase impulse convturn seize idle markers.

marker 500, over conductor 2|8 to the armatures of all relays of the registers 20| and 202. The operation of relay 201 also closes a circuit from ground over conductor 2 6 and through the Winding of relay 500 of the marker 500. Relay506 operates and prepares the receiving tubes 503 and 504 'for receiving the signal impulses from-the sender. Thus the' sender 200 has been seized by the calling line |08, and the sender in turn has appropriated or seized the rst idle marker, namely, the No. marker 500. The seized marker 500 is guarded against seizure by other senders by the operation of therelays 308, 400,'etc., in said other senders.

The calling subscriber |08 now proceeds to operate his dial to send the wanted designation to the sender 200, including the ofce code digits and the usual numerical digits. The two code digits cause the operation of the registers. 20| and 202m the Well-known manner,and a -combination of the relays of these registers are operated to`reg`ister the particular digits involved. Assume that the oilice code is represented bythe digits 3 5, in which case the relay 2 I0 of register 20| and relay 220 of register 202 are operated, and all of the other relays of these registers re- Vmain deenergized.

It Will alsobe assumed that the subscriber of another line, such as line |09, initiates a call at about this time. Line |00 is extended over the line switch |00 to an idle junctor l0 and through the sender selector switch |00 to the next idle 1 sender in the group, such as the sender 300. The

seizure of sender 300 causes the closure of the start circuit over conductor 3| back contacts of relay 312, assuming the third or No. Zvrnarker 600,to which relay 3|2 is individual, isidle, Wind ing of relay 3|3, conductor 3|4, normal contacts of relay 22| to battery; Relay 3|3 operates in this circuit andcloses a circuit from ground through its inner upper front contact, `resistor 355, thence over conductor 3|6 andv over multiple circuits toA battery through the windings of relays 2l3, 400, etc., to render the marker 600 nonselectable tothe allotter circuits 205, 405, etc., of

' the senders. The groundedconductor SI5 is also ing tubes for receiving the signal impulses from the sender 300. Thus a second sender 300 has been seized concurrently With the seizure of the rst sender 200, and the second sender has appropriated a second idlemarker 500. If other calls arrive during this period, other senders are seized to serve these calls, and `these senders in In other Words, a plurality of senders and associated markers may -be in useconcurrently, and the records established in these senders may be transferred during the common seizure period over the common transmitting medium 20| Without interference.

.As soon following theoperation of the register relays 2.!9 and 220 as the generator 540 reaches lits No. 0 phase, a positive impulse of this phase From the tubes 222 and 223 the impulse circuits,

Relay 3|3 connects the phase vim- Y delivered to the tube 5H.

may be traced over conductors l220 and 221 and thence through resistors 501 and 508 to the control electrodes 509 and 5|0 of receivingtubes 5|| and 5|1, respectively. From the tubes 224 yand 225 the impulse circuits may be traced over the conductors 22S and 229 through resistors 521and 528 to the control electrodes of tubes 529 and 30 of the group 504. At the same time a negative impulse of No. 0 phase is applied over conductor 540 through the contacts of relay 500` and thence through resistors 5|3 and 5|4 to the control electrodes 5|5 and 5|6, respectively, and also through the resistors 53| and 532 to the control electrodes of the tubes 529 and 530, respectively. The sum of the positive and the negative impulses applied to the control electrodes of tubes 5| I, 5|1, 529 and 530 is suiiicient to ionize their control gaps.

Generator 5|8 supplies current to the anodes of the tubes 503 and 504, and it is in phase With the impulses delivered to the impulse conductor 541. Therefore, each time the control gap S-5| 5 of tube 5| ionizes, current oWs from the generator 5|3 through the winding of slow-release relay 5|0, anode 520, cathode 52| to the negative pole of battery 52 2; These successive impulses owing through the relay 5| 9 operate it and hold it infits operated position as long as ionizing impulses are In like mannerthe tube 5|1 ionizes in response to the application thereto of impulses of phase No. 0, and current ows from the generator 5|8 through the winding of slow-release relay 523, anode and cathode of tube 5|'l tothe negative pole of battery 522. Relay 523 operates, and the circuit may be now traced from ground through the front contacts of the operated relay 5|9 through the back contacts of relays 524 and 525, front contacts of relay i 523, back contacts of relay 526 thence over conductor 521 to the route and control-mechanism 505.

In like manner the tubes 529 and 530 of the group 504 ionizle and current ilovvs from the generator 5|8 to the slow-release relays 533 and 534, anodes and cathodes of tubes 529 and 530 to the negative pole of battery 535. `Re1ays 533 and 534 operate and close a circuit which may be traced from ground over conductor 535to the mechanism 505. Thus the grounded conductors 521 and 530 cause the selection and operation 'of relays in the mechanism 505 to indicate theroute represented by the code designation 3 5.

Concurrently with l,the transfer of `theregis tration from sender 200 to marker 500 the registration in sender 300 is also transmitted over the common medium 2|0 to the associated marker 000. As above explained, the registration from sender 200 is transmitted by impulses of phase No, 0 delivered by the impulse circuit 542. lThe registration in sender 300 is transferred by impulses of phase No. 2, which are delivered bythe impulse circuit 544. Each time, therefore,A the generator 540 enters its. No. 2 phase positive impulses are transmitted over conductor 553 thence through the closed contacts of relay 3|3 inthe 'sender,300, representing the seized marker 600,

conductor 321 through the contacts of the joperated register relays 30I, 302, thence through a set of transmitting tubes similar to tubes 203 and 204 to the corresponding conductors 2|0. These positive impulses appearing on conductors 2|0 are applied to the starting electrodes of the receiving tubes o f all markers, including the tubes of theassociated marker 000. At the same' time negative impulses of the o. 2 phase are applied over conductor 554 through the contacts of relay 505 to the other control electrodes of the receiving tubes of marker 600. The tubes of marker B operate to the exclusion of the tubes of any other marker, and the registration of the sender 300 is transferred to the. marker 600 where it causes the operation of a route relay or other device representing the destination of the call.

In like manner any number of simultaneous connections may be made between senders and associated markers andthe individual registrations transferred over the common medium 2|0 without mutual interference. i

Following the operation of a route relay in the routing and controlling mechanism 505 of the marker 500, this marker connects itself through frame connectors Ill and |I2 with the district and oice selectors |02 and |04, and these switches are operated to extend the calling line |08 over the junctor |0|, junctor |03 to an idle one of the outgoing trunks |05.

At the proper time in the sequence of controlling operations the start conductor 2|| in the sender 200 is opened to permit therelease of relay 201. The release of relay 201 opens the wire 2| Iis grounded in the process oi making a new selection of anl idle marker. lThisis an old and well-known feature in start wire circuits; Also provision may be made ,for opening the start' wire in case a new` call comes in when all marker allotter relays are energized. This makes it possible for one of the relays to release as soon as a busy marker becomes idle.

What is claimed is:

1. The combination in a signaling system of a group of sending mechanisms and a group of receiving mechanisms, each of said mechanisms having means for registering information therein, a common signaling medium permanently connecting all of said sending mechanisms with all of said receiving mechanisms, means for seizing said sending mechanism for use, means for causing each one of said sending mechanisms taken in use to lseize any idle ene of said receiving mechanisms, means for producing signaling currents, onev for each of said receiving mechanisms, each of said currents having adiiferent characteristic,

means for sending over `saidcommon mediumV fromsaid sending mechanisms to al1 of said receiving mechanisms the signal currents charac- 1 terizing respectively the seized'receiving mechaholding circuits of relays 308, 408, etc., and these f relays release to render the marker 500 free for subsequent selection by one of the senders. Also at the proper time the sender 200 is released, and the sender selector switch normal condition.

Once per -cycle of the generator 54| a test is made of the common transmitting conductors 2|0. This test is made by impulses delivered by the circuit 549, which may occur in the No. 8 phase position of the generator 540. Each time the generator enters the No. 8 phase position positive impulses are transmitted over conductor 552 through the ten tubes 6 |5 thence to the corresponding ten conductors of themedium 2|0. vThese impulses are transmitted over the conductors 2|0 toward the markers where they are applied through resistors 600 to the starting electrodes 606, 601, etc., of the ten tubes 6|0. At

|06 is restored to its the same time impulses of negative polarity of phase No. 8 are applied over conductor 55| through resistors 609, 6|| to the corresponding start electrodes of the ten tubes 6 0. These tubes all ionize, provided the conductors 2|0 are intact and the positive impulses all appear on the electrodes of the tubes. When tube 6|2 ionizes, a circuit is closed from the generator 6|3, which is in its positive half cycle when the generator 540 is in its No. 8 phase, winding of slow-release relay 503, anode and cathode of tube SI2 to the negative pole of battery 6M. Discharge current flows in this circuit, and relay 603 operates and attracts its armature. Likewise each of the other tubes discharges, and the corresponding relay in ythe anode circuit Operates to attract its armature. As long as all of the relays 603, 604, etc., are energized the circuit of alarm relay 6 I6 is maintained open. As soon, however, as any one of the conductors 2|0 fails to deliver animpulse to `the corresponding tube `charge its main gap, and the corresponding relay releases *its armature. The released relay closes an obvious circuit for energizing the alarm relay BIB. The alarm relay BIB gives notice to the exchange attendant that trouble exists in the transmitting conductors 2 |0.

It will be noted that the marker allotting relays 206, 208, etc., have locking windings which serve to prevent them from releasing while the start 6 l0, this tube fails to diS- nisms to transferthe information registered in the respective associated sending mechanisms, and means in each receiving mechanismforselecting from said common medium the signaling current of the corresponding characteristic to register therein the information transferredfrom the associated sending mechanism.

2. The combination in a signaling system of a group of sending devices, a group of receiving devices, each of said devices having means for registering information therein, a common signaling medium connecting all of said sending devices with all o said receiving devices, means for seizing said sending devices for use, means for effecting coexisting seizures between the sending devices concurrently in use and respective ,idle ones v of said receiving devices, any one of said sending devices being capable of seizing any idleone of said receiving devices, means for producing signaling currents of different characters, said currents representing respectively'the receiving devices, means for sending over said common medium from said sending devices to said receiving devices the signal currents representing the 'for registering information therein, a vcommon signaling `medium permanently connecting said sending devices with said receiving devices, means for seizing said sending devices for use, means for effecting coexisting seizures between .the sending devices concurrently in use and respective idle ones of said receiving devices, a source of alternating current, means for producing in each cycle of said source a plurality of impulses of successive phases, said phases characterizing respectively said receiving"` devices, means for sending over said common medium within a cycle of said source phase impulses characterizing the seized receiving devices for vthe purpose of transferring over said medium the information registered in all of the associated sending devices, and means in each receiving device for selecting from said common medium the signal impulses of the corresponding phase to register therein the infomation transferred from the associated sending device.

4. The combination in a signaling system of a plurality of sending devices, a plurality of receiving devices, each of said devices having means for registering information therein, a common signaling medium permanently connecting said sending devices with said receiving devices, means for seizing said sending devices for use, means for effecting coexisting seizures between the sending devices concurrently in use and respective idle ones of said receiving devices, a source of alternating current, means for producing in each cycle of said source a plurality of impulses of successive phases, said phases characterizing respectively said receiving devices, means for sending over said common medium within a cycle of said source phase impulses characterizing each seizedreceiving devices and in codes representing the information in the sending device that has seized said receiving device, and means associated with each receiving device for selecting the code impulses of the phase characterizing said receiving device to register therein the information transferred from the sending device.

5. The combination in a signaling system cf a group of sending devices, a group of receiving devices, each of said devices having means for establishing signaling information therein, a `common signaling conductor joining all of said sending devices in a continuous connection with all of said receiving devices, means for seizing a variable number of said sending devices for concurrent use, means for causing each one of the sending devices taken in use to seize any idle one of said receiving devices, means for producing signalling currents of different ,characteristics, said currents serving respectively the receiving devices, means for sending over said common signaling conductor from said sending devices to said receiving devices the signaling currents characterizing respectively the seized receiving devices for the purpose of transferring the .information established in the respective sending devices, and means in each receiving device for selecting from said` common signaling .conductor the signaling current of the corresponding characteristic to establish therein the information transferred from the associated sending device.

6. The combination in a signaling system of a group of sending devices, a group of receiving devices, means in each of said devices for registering signaling information, a common signaling conductor joining all of said sending devices in a continuous connection with all of said receiving devices, means for seizing a variable number of said sending devices for concurrent use, means for causing each sending device taken in use to seize the next idle one of said receiving devices, means for producing impulses of a plurality of phases, said phases corresponding respectively with said receiving devices, means for sending over said signaling conductor from each of the sending devices in use impulses of the phase corf responding to the seized receiving devices for the purpose of transferring over said conductor the information registered in all of the sending devices in concurrent use, and means in each re-4 sponding phase to register in said receiving de-i vice the information transferred sociated sending device,

7. The combination in a switching system of a group of senders, a group of switch controlling markers, each of said senders and markers `having means therein for registering signal information, a common signaling conductor permanently joining each of said senders with each of said markers, means for seizing a variable number of said senders for use, means for effecting coexisting seizures between the senders taken in use and respective idle ones of said markers, means for producing signaling currents of different characters, said signaling currents serving respectively the different markers, means for sending over said common conductor from the senders to the markers signaling currents representing the seized markers for the purpose of transferring over said conductor the information registered in the senders in use, means for each of said markers for selecting from said common conductor the signaling current of the corresponding characteristic for registering in said marker the information transferred from the associated sender, automatic switches, and means controlled by said markers in accordance with the information registered therein for causing the selective operation of said switches.

8. The combination in a switching system of a group of senders, a group of switch controlling markers, means in said senders and markers for registering signaling information, a common signaling medium connecting all of said senders with all of said markers, means for seizing a number of said senders for concurrent use, means for causing each one of the senders taken in use to seize an idle one of said markers, means for sending signaling currents over said common medium to transfer the information registered in the senders to the associated seized markers, and means for continuously applying impulses to said signaling medium to determine if it is in condition for the transmission of said signaling currents from the senders to the markers.

9. The combination in a switching system of a group of senders, a group of switch controlling markers, means in said senders and markers for registering signaling information, a group of signaling conductors joining in a permanent and continuous connection all of said senders and markers, means for seizing a number of said senders for concurrent use, means for causing each one of the senders taken in use to seize an idle one of said markers, means for sending signaling impulses of a plurality of different phases over said signaling conductors to transfer the information registered in said senders to the associated seized markers, and means for sending impulses of a phase other than the phases used for said signaling impulses over said conductors for determining whether they are in condition for the transmission of the signaling impulses between the senders and the markers. 1

from the as- WILLIAM T. HOLDEN. 

